PROJECT SUMMARY/ABSTRACT Histone genes are frequently mutated in cancer, but the significance of most histone mutations is unknown and few strategies to therapeutically target tumors harboring histone mutations have been developed. Histones are a fundamental component of chromatin, which regulates the accessibility of DNA for gene expression through dynamically regulated combinatorial post-translational modifications (PTMs) of histones? N-terminal tails. Classical oncogenic histone (?oncohistone?) mutations directly prevent the ?writing? of some of these PTMs, promoting oncogenesis through altered transcription patterns that inhibit differentiation. The PI and his collaborators have recently characterized an unexpectedly broad landscape of novel oncohistone mutations that occur in roughly 4% of tumors. The goal of the proposed work is to understand the impact of a subset of these novel oncohistones on chromatin and tumor biology and to develop strategies to therapeutically target tumors expressing oncohistones. Preliminary data presented in this proposal show (a) that a class of novel oncohistone mutations at H3 N-terminal arginine (H3R) residues alter nearby regulatory PTMs and impair cellular differentiation, and (b) that differentiation blockade driven by the classical H3K36M oncohistone mutation can be rescued by tyrosine kinase inhibition. Therefore, experiments are proposed to test the hypotheses that H3R oncohistone mutations disrupt the chromatin landscape, alter transcription, and dysregulate cellular functions, and that tyrosine kinase signaling mediates oncohistone-induced differentiation blockade. To rigorously test these hypotheses, experiments are proposed to (1) elucidate the effects of novel oncohistone mutations on the chromatin landscape and chromatin-dependent transcription, differentiation, and tumorigenesis and (2) determine how inhibition of kinase signaling rescues classical oncohistone-induced differentiation blockade. The proposed work will improve understanding of cancer-associated histone mutations and may lead to the development of new genotype-directed cancer therapies. The PI, a Medical Oncology Fellow at Memorial Sloan Kettering Cancer Center (MSKCC), has developed a 5-year career development plan that builds upon his scientific background in chemical biology and clinical training in medical oncology. He will conduct the proposed research under the mentorship of Dr. C. David Allis, an internationally recognized expert in oncohistone mutations and epigenetics, and will develop new skills in chromatin biology including chromatin-relevant bioinformatics and biochemistry that are critical for his future career focused on understanding and therapeutically targeting epigenetically driven cancers. This training, combined with his background, mentorship, and the institutional environment of MSKCC and partner institution The Rockefeller University, positions the PI to successfully transition to independence as an academic physician-scientist with his own laboratory and grant funding.